From a1081ea79c8bdfaabb286e530648461188c73910 Mon Sep 17 00:00:00 2001
From: Alex Zenla <alex@mycelium.engineering>
Date: Tue, 30 Jan 2024 02:05:37 -0800
Subject: [PATCH] xenevtchn: convert to using thiserror

---
 xen/xenclient/src/lib.rs         |  5 ++-
 xen/xenevtchn/Cargo.toml         |  1 +
 xen/xenevtchn/examples/simple.rs |  5 +--
 xen/xenevtchn/src/error.rs       | 11 ++++++
 xen/xenevtchn/src/lib.rs         | 57 ++++++--------------------------
 5 files changed, 27 insertions(+), 52 deletions(-)
 create mode 100644 xen/xenevtchn/src/error.rs

diff --git a/xen/xenclient/src/lib.rs b/xen/xenclient/src/lib.rs
index dc8fc78..c3dc8c2 100644
--- a/xen/xenclient/src/lib.rs
+++ b/xen/xenclient/src/lib.rs
@@ -19,7 +19,6 @@ use std::time::Duration;
 use uuid::Uuid;
 use xencall::sys::CreateDomain;
 use xencall::{XenCall, XenCallError};
-use xenevtchn::EventChannelError;
 use xenstore::client::{
     XsPermission, XsdClient, XsdInterface, XS_PERM_NONE, XS_PERM_READ, XS_PERM_READ_WRITE,
 };
@@ -78,8 +77,8 @@ impl From<FromUtf8Error> for XenClientError {
     }
 }
 
-impl From<EventChannelError> for XenClientError {
-    fn from(value: EventChannelError) -> Self {
+impl From<xenevtchn::error::Error> for XenClientError {
+    fn from(value: xenevtchn::error::Error) -> Self {
         XenClientError::new(value.to_string().as_str())
     }
 }
diff --git a/xen/xenevtchn/Cargo.toml b/xen/xenevtchn/Cargo.toml
index faf62e9..1e05e6c 100644
--- a/xen/xenevtchn/Cargo.toml
+++ b/xen/xenevtchn/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2021"
 resolver = "2"
 
 [dependencies]
+thiserror = { workspace = true }
 log = { workspace = true }
 
 [dependencies.nix]
diff --git a/xen/xenevtchn/examples/simple.rs b/xen/xenevtchn/examples/simple.rs
index 651b441..85d6b43 100644
--- a/xen/xenevtchn/examples/simple.rs
+++ b/xen/xenevtchn/examples/simple.rs
@@ -1,6 +1,7 @@
-use xenevtchn::{EventChannel, EventChannelError};
+use xenevtchn::error::Result;
+use xenevtchn::EventChannel;
 
-fn main() -> Result<(), EventChannelError> {
+fn main() -> Result<()> {
     let mut channel = EventChannel::open()?;
     println!("Channel opened.");
     let port = channel.bind_unbound_port(1)?;
diff --git a/xen/xenevtchn/src/error.rs b/xen/xenevtchn/src/error.rs
new file mode 100644
index 0000000..6c5f7b5
--- /dev/null
+++ b/xen/xenevtchn/src/error.rs
@@ -0,0 +1,11 @@
+use std::io;
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("kernel error")]
+    Kernel(#[from] nix::errno::Errno),
+    #[error("io issue encountered")]
+    Io(#[from] io::Error),
+}
+
+pub type Result<T> = std::result::Result<T, Error>;
diff --git a/xen/xenevtchn/src/lib.rs b/xen/xenevtchn/src/lib.rs
index 15d0a8c..165362c 100644
--- a/xen/xenevtchn/src/lib.rs
+++ b/xen/xenevtchn/src/lib.rs
@@ -1,9 +1,9 @@
+pub mod error;
 pub mod sys;
 
+use crate::error::Result;
 use crate::sys::{BindInterdomain, BindUnboundPort, BindVirq, Notify, UnbindPort};
-use nix::errno::Errno;
-use std::error::Error;
-use std::fmt::{Display, Formatter};
+
 use std::fs::{File, OpenOptions};
 use std::os::fd::AsRawFd;
 
@@ -11,45 +11,8 @@ pub struct EventChannel {
     pub handle: File,
 }
 
-#[derive(Debug)]
-pub struct EventChannelError {
-    message: String,
-}
-
-impl EventChannelError {
-    pub fn new(msg: &str) -> EventChannelError {
-        EventChannelError {
-            message: msg.to_string(),
-        }
-    }
-}
-
-impl Display for EventChannelError {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.message)
-    }
-}
-
-impl Error for EventChannelError {
-    fn description(&self) -> &str {
-        &self.message
-    }
-}
-
-impl From<std::io::Error> for EventChannelError {
-    fn from(value: std::io::Error) -> Self {
-        EventChannelError::new(value.to_string().as_str())
-    }
-}
-
-impl From<Errno> for EventChannelError {
-    fn from(value: Errno) -> Self {
-        EventChannelError::new(value.to_string().as_str())
-    }
-}
-
 impl EventChannel {
-    pub fn open() -> Result<EventChannel, EventChannelError> {
+    pub fn open() -> Result<EventChannel> {
         let file = OpenOptions::new()
             .read(true)
             .write(true)
@@ -57,14 +20,14 @@ impl EventChannel {
         Ok(EventChannel { handle: file })
     }
 
-    pub fn bind_virq(&mut self, virq: u32) -> Result<u32, EventChannelError> {
+    pub fn bind_virq(&mut self, virq: u32) -> Result<u32> {
         unsafe {
             let mut request = BindVirq { virq };
             Ok(sys::bind_virq(self.handle.as_raw_fd(), &mut request)? as u32)
         }
     }
 
-    pub fn bind_interdomain(&mut self, domid: u32, port: u32) -> Result<u32, EventChannelError> {
+    pub fn bind_interdomain(&mut self, domid: u32, port: u32) -> Result<u32> {
         unsafe {
             let mut request = BindInterdomain {
                 remote_domain: domid,
@@ -74,7 +37,7 @@ impl EventChannel {
         }
     }
 
-    pub fn bind_unbound_port(&mut self, domid: u32) -> Result<u32, EventChannelError> {
+    pub fn bind_unbound_port(&mut self, domid: u32) -> Result<u32> {
         unsafe {
             let mut request = BindUnboundPort {
                 remote_domain: domid,
@@ -83,21 +46,21 @@ impl EventChannel {
         }
     }
 
-    pub fn unbind(&mut self, port: u32) -> Result<u32, EventChannelError> {
+    pub fn unbind(&mut self, port: u32) -> Result<u32> {
         unsafe {
             let mut request = UnbindPort { port };
             Ok(sys::unbind(self.handle.as_raw_fd(), &mut request)? as u32)
         }
     }
 
-    pub fn notify(&mut self, port: u32) -> Result<u32, EventChannelError> {
+    pub fn notify(&mut self, port: u32) -> Result<u32> {
         unsafe {
             let mut request = Notify { port };
             Ok(sys::notify(self.handle.as_raw_fd(), &mut request)? as u32)
         }
     }
 
-    pub fn reset(&mut self) -> Result<u32, EventChannelError> {
+    pub fn reset(&mut self) -> Result<u32> {
         unsafe { Ok(sys::reset(self.handle.as_raw_fd())? as u32) }
     }
 }